Conventionally, there is known an illumination system which uses a human body sensing sensor, and which is lit with high illuminance when it is sensed that a person is present, and which is lit with low illuminance or lit OFF when it is sensed that a person is absent (for example, see Patent Document 1).
FIG. 25 is a view showing a schematic configuration of such an illumination system. Referring to the drawing, a signal indicative of the presence/absence of a person detected by a human body sensing sensor 31 is sent to a sensor control block 32. As shown in FIG. 26, for example, the signal indicative of the presence/absence of a person is a pulse signal which is at the H level when a person is sensed and which is at the L level when a person is not sensed. When the signal is input, for example, the sensor control block 32 outputs a dimming signal which is pulse width modulated (PWM) such as shown in FIG. 27, to an illumination lighting apparatus 33 such as an electronic ballast.
When a person is sensed, as shown in FIG. 27(A), a PWM signal having a duty of 5% by which a discharge lamp 34 is fully lit is output to the illumination lighting apparatus 33, and, when a person is not sensed, as shown in FIG. 27(B) and (C), a PWM signal having a duty of 100% by which the discharge lamp 34 is lit OFF, or that having a duty of 85% by which the discharge lamp is lit with low illuminance is output to the illumination lighting apparatus 33.
The sensor control block 32 sets also a lighting holding time after a person is sensed, and a controls the discharge lamp 34 so that it is not lit OFF immediately after a person is absent, but holds lighting for, for example, several minutes as shown in FIG. 28. This control is preformed because of the following reason. In an illumination system for a stairway or the like, when a lamp is lit OFF immediately after a person is absent, for example, it is sometimes difficult to ascend or descend stairs.
Moreover, there is an illumination system in which the ambient brightness due to daylight is detected by using an illuminance sensor, and an illumination apparatus is automatically controlled to an appropriate light amount in accordance with the detected brightness. In the illumination system, when it is light outdoors, the illumination apparatus is lit with low illuminance, and, when it is dark outdoors, the illumination apparatus is lit with high illuminance, thereby obtaining an illumination environment where the brightness is always constant (for example, see Patent Documents 1 and 2).
FIG. 29 is a view showing a schematic configuration of an illumination system using an illuminance sensor. Referring to the figure, a brightness signal which is detected by an illuminance sensor 41, or, for example, a DC signal which, as shown in FIG. 30(A) and (B), when it is light, is 5 V, and, when it is dark, is 1 V is sent to a sensor control block 42. In accordance with the signal input from the illuminance sensor 41, the sensor control block 42 outputs, for example, a PWM dimming signal such as shown in FIG. 31, to an illumination lighting apparatus 43.
In the case where the illuminance sensor 41 detects that the ambient brightness is dark, a PWM signal having a duty of 5% by which the discharge lamp 34 is fully lit is output to the illumination lighting apparatus 43 as shown in FIG. 31(A), and, in the case where it is detected that the ambient brightness is light, a PWM signal having a duty of 85% is output to the illumination lighting apparatus 43 as shown in FIG. 31(B) to dim so that the optical output of the discharge lamp 34 is reduced. In accordance with the ambient brightness detected by the illuminance sensor 41, for example, the space illuminance can be controlled so as to be substantially constant at any time of the day or night as shown in FIG. 32. When the relationship between the output signal of the illuminance sensor 41 and the dimming signal of the sensor control block 42 is arbitrarily adjusted, it is possible to change the space illuminance to be controlled.
Furthermore, there is an example of a dimmer in which, in order to arbitrarily adjust the brightness of an illumination environment, a PWM signal is output to an illumination lighting apparatus.
FIG. 33 is a view showing a schematic configuration of an illumination system in which the brightness of an illumination environment is controlled by using a dimmer. Referring to the figure, a PWM signal which is output from a dimmer 51 is input to an illumination lighting apparatus 53. In the case where the ON duty ratio of the PWM signal is small as shown in FIG. 34(A), the illumination lighting apparatus 53 increases the optical output of the discharge lamp 34, and, in the case where the ON duty ratio is large as shown in FIG. 34(B), the illumination lighting apparatus 53 decreases the optical output of the discharge lamp 34. In the case where the ON duty ratio is 100% as shown in FIG. 34(C), the illumination lighting apparatus 53 lights OFF the discharge lamp 34. In this way, a person adjusts the volume of the dimmer 51 to change the duty ratio of the PWM signal which is output from the dimmer 51, whereby desired illuminance can be obtained.
As described above, in a conventional illumination system in which external apparatuses such as a human body sensing sensor, an illuminance sensor, and a dimmer are used, signal modes and illumination controls such as lighting-ON, lighting-OFF, and dimming are different, and hence it is usual to individually dispose sensor control blocks which correspond thereto, respectively.
When a sensor control block is individually disposed for each of external apparatuses, the cost is increased, and a problem in that the general versatility is poor is caused.